WO2012/041872 discloses novel N-heteroaryl compounds that are useful as medicaments. This patent application also discloses the dehydration of ethyl 4,4,5,5-tetrafluoro-3-hydroxy-pentanoate to ethyl (E)-4,4,5,5-tetrafluoropent-2-enoate using phosphorous pentoxide (P2O5).

WO2012/041873 discloses novel N-heteroaryl compounds that are useful as medicaments. This patent application also discloses the dehydration of ethyl 4,4,5,5,5-pentafluoro-3-hydroxy-pentanoate to ethyl (E)-4,4,5,5,5-pentafluoropent-2-enoate using phosphorous pentoxide (P2O5).

WO2013/144179 discloses novel heteroaryl compounds that are useful as medicaments. This patent application also discloses the dehydration of ethyl 4,4 difluoro-3-hydroxy-pentanoate to ethyl (E)-4,4-difluoropent-2-enoate using diphenyl-2-pyridylphosphine and di-butylazodicarboxylate.
WO2013/144180 discloses novel heteroaryl compounds that are useful as medicaments. This patent application also discloses the dehydration of ethyl 4,4 difluoro-3-hydroxy-pentanoate to ethyl (E)-4,4-difluoropent-2-enoate using diphenyl-2-pyridylphosphine and di-butylazodicarboxylate.

Jagodzinska et al. Tetrahedron 63 (2007) 2042-2046 discloses the synthesis of crotonic acid analogues according to the following route:
wherein the dehydration reaction from C to D, the reagent used was P2O5. Moreover, this reference discloses that this reaction was also attempted using mesyl chloride and triethylamine for the transformation of C to D. However, the desired product (D) was only obtained as a minor product in a mixture of carboxylic acids. H2SO4, H2SO4/AcOH, SOCl2 and DBU/CHCl3 were also unsuccessfully used as reagents for the dehydration reaction. R═F, H, CF3, Cl, Br, or I.
Bevilaqua, J. Org. Chem. 49 (1984) 1430-1434 discloses a dehydration reaction using triphenylphosphine and diethyl azodicarboxylate (DEAD) as reagents.

Tamura et al. Journal of Fluorine Chemistry 126 (2005) 918-930 discloses a dehydration reaction using tosyl choride and triethylamine (TEA)

Yamazaki et al., Tetrahedron: Asymmetry 1 (1990) 521-524 also discloses a dehydration reaction using tosyl choride and triethylamine (TEA).
